Power looms, for forming sheds or shedding, have heddle shafts with heddles that are retained on support rails. In operation, the heddle shafts are moved back and forth for shedding. With increasing operating speed of the power looms, the shedding must be done faster and faster, which leads to high dynamic loads on the heddle support rails and the heddles.
Shedding using heddle shafts on which heddles are retained is an old fundamental principle that has been employed for a long time. For instance, U.S. Pat. No. 2,047,511 discloses one such heddle shaft, which forms a rectangular frame. The upper and lower beams extending transversely to the direction of motion of the heddle shaft are called the shaft rod. Parallel to each of the two shaft rods is a respective heddle support rail, whose ends are retained on the side struts, connecting the shaft rods, of the heddle shaft. C-shaped end eyelets of heddles are seated on the heddle support rails and disposed in relatively large numbers parallel to one another in the heddle shaft.
A further fundamentally similar prior art is embodied by the heddle shaft described in Swiss Patent CH 402 767, on the heddle support rails of which heddles with J-shaped end eyelets are seated. In operation, the frame formed of the shaft rods and the side struts, like the heddle support rails, is subjected to dynamic deformation, which depending on the flexibility or rigidity of the arrangement and on the operating speed can become considerable. This deformation has the effect that under dynamic load, the spacings between the heddle support rails are not constant but instead locally vary. To keep these factors away from the heddles, the heddles are seated on the heddle support rails with considerable play.
The need to create relatively sturdy heddle support rails on the one hand and on the other to support the heddles with adequate play on the heddle support rails is reflected in ISO 11677-1, which for C-shaped end eyelets of weaving heddles prescribes an inner clearance height of 26.7 mm. The inner breadth of the end eyelet is 2.5 mm. These dimensions apply to heddle support rails which at present have a height of 22 mm and a breadth of 1.7 mm. Thus the heddles have more than 4 mm of play in the longitudinal direction and approximately 0.8 mm in the transverse direction.
The need at present is to design heddle shafts that are substantially stiffer than before, so that the expected dynamic deformations occur only at substantially higher operating speeds that before. However, these dynamic deformations can never be avoided entirely, because of the masses that must be accelerated and braked, which are brought to bear by the heddle shaft itself and by the heddle support rails, the heddles, and the warp yams that pass through the heddles.
With this as the point of departure, it is the object of the invention to improve the heddle shaft and the weaving heddles in such a way that higher operating speeds can be attained.